IPhone : is there a way to sort an array by category on ios

How can I create a custom sort order on my app? Suppose that I have a company and my workers are divided by positions inside the factory and I wanna see the performance of my workers on a specific position. I could, on core Data, predicate a result for that but I wanna, at the same time, see more than one positions, like constructor, driver, engineer, etc. How can I order the fetch request so that the result it should be all of constructors first, the all the drivers and at the end of all of the engineers?

Thanks in advance and I hope that I explained what I want.